Many radio communication systems are configured to transmit and receive from the same antenna, because it is simply more efficient in some ways to use one antenna versus two. Further efficiencies are achievable if the transmission and reception can occur simultaneously on the same radio channel, which is often referred to as full-duplex transmission.
In full-duplex transmission, simultaneous transmission and reception may be carried out on a common frequency channel using a common antenna. One difficulty in full-duplex transmission is self-interference induced at the receiver by a transmitted signal. A typical approach to mitigating the self-interference is to use interference cancellation of the known transmitted signal. The interference cancellation is often accomplished in several stages, which can include passive analog cancellation, active analog cancellation, and digital cancellation.